Wiring whole car

JacobM03

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1992 Thunderbird Sport 5.0
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I am planning on rewiring my whole car as I am switching over to Holley sniper efi and would like to remove as much wiring as I can and reroute the wiring to make things alot cleaner.

Will also be moving battery to the trunk and making a custom fuse panel.

Has anyone already done this or does anyone have any tips or information on doing this?
 
The factory body wiring for stuff like lights, door locks, windows, mirrors, speakers, fuel pump/sender is routed fairly efficiently, so if the goal is to clean things up you’ll likely be disappointed in what you can accomplish unless you plan to strip features.

What year is your car? 97s in particular have just about perfect of a harness layout, whereas say a 94 is a little wacky with ABS, EVO, premium sound wiring running through the interior channels in separate harnesses front to back. 96 and 97 consolidated and simplified that stuff into the main harnesses with modules relocated closer to the sensors/components they operate. I rewired my 94 to 97 spec pretty thoroughly

These cars don’t use canbus or BCMs so no worries there but I strongly recommend getting a Ford EVTM book to guide you through the various circuit paths. I’d adhere particularly closely to the factory ground junctions so as to not create ground loops.
 
I guess the first question I have is why are you going from the factory 302 EFI to an aftermarket setup? Not knocking the choice, just trying to understand what you are wanting to get from it.

Get an EVTM for 1992 and start studying it. On a 1992 302, you've got the mechanically-operated AOD transmission, so you won't have to worry about any of that. Personally, I would relocate the battery and leave all the other electrics intact. There's not really much to "clean up" on these cars, especially if you don't have ABS or other luxury options.
 
The factory body wiring for stuff like lights, door locks, windows, mirrors, speakers, fuel pump/sender is routed fairly efficiently, so if the goal is to clean things up you’ll likely be disappointed in what you can accomplish unless you plan to strip features.

What year is your car? 97s in particular have just about perfect of a harness layout, whereas say a 94 is a little wacky with ABS, EVO, premium sound wiring running through the interior channels in separate harnesses front to back. 96 and 97 consolidated and simplified that stuff into the main harnesses with modules relocated closer to the sensors/components they operate. I rewired my 94 to 97 spec pretty thoroughly

These cars don’t use canbus or BCMs so no worries there but I strongly recommend getting a Ford EVTM book to guide you through the various circuit paths. I’d adhere particularly closely to the factory ground junctions so as to not create ground loops.
Didn't see this before I posted my comment. Great minds think alike. :rofl:
 
Are the 5.0's in these port injection or TB injection?
 
Are the 5.0's in these port injection or TB injection?
It is port injection on the MN12 302.

The non-High Output Lincoln 302 got TBI in 1980. Ford and Mercury followed suit in 1983. The 5.0 HO debuted shortly after with port EFI for the Mustang GT and Capri RS 302. The rest of the FoMoCo lineup got port EFI for both HO and non-HO 302's in 1986.
 
Never owned a 5.0, but I've worked on an 85 carbed one, and a 91, which I thought was tbi, but idk. We were replacing the clutch, lol.
 
GT 5 speeds were carbed in 85, but 91 CFI was long gone. GM had a few engines still utilizing that junk in the 90s
 
I'm curious if this is a factory 302 Tbird or if he is doing an engine swap.
 
GT 5 speeds were carbed in 85, but 91 CFI was long gone. GM had a few engines still utilizing that junk in the 90s
IIRC, the Capri RS 302 got fuel injection in 1984 while the Mustang didn't get it until 1986.

I do know all the RS Turbos and ASCs had EFI regardless of year.
 
IIRC, the Capri RS 302 got fuel injection in 1984 while the Mustang didn't get it until 1986.

I do know all the RS Turbos and ASCs had EFI regardless of year.
I have an 85 Capri RS 5.0. It was the last year for the Carb, first year for the roller cam. 1986 was the first year for the 5.0 fuel injection for both the Capri RS and the Mustang GT.
 
You're right. The ASC had it in 1985 but there's only 257 of those. There's also an ASC pace car of which I think only 50 were made.

Dad had a 1979 before the bubbleback was introduced. Black over tan with the 4MT and TRX wheels. I'd kill to have a RS 302.
 
You're right. The ASC had it in 1985 but there's only 257 of those. There's also an ASC pace car of which I think only 50 were made.

Dad had a 1979 before the bubbleback was introduced. Black over tan with the 4MT and TRX wheels. I'd kill to have a RS 302.
Man, I had two of them! an 84 and the 85, Sold the 84 about 7 years ago. TRX wheels are neat.
 
Lots more details needed on what you're trying to accomplish. What motor, fuel injection type, etc.
 
Agreed that the '97 harness is an efficient design as-is.

That said, any time I wire a car from scratch, I draw up a schematic in CAD, then edit as necessary as I go along. Figure out your connectors, wire colors, gauges, etc. on paper before you start.


This isn't the best image, but it's what I have at the moment. You can see the schematic hanging on the side of my F150 for the sand rail I was wiring.

IMG_2739.JPG
 
I have an 85 Capri RS 5.0. It was the last year for the Carb, first year for the roller cam. 1986 was the first year for the 5.0 fuel injection for both the Capri RS and the Mustang GT.
They had CFI earlier, 83 or 84 IIRC, but it depended on the transmission. 85 5 speeds were carbed/roller, 85 autos were CFI/flat tappet. 86 switched to multiport SEFI for both
 
They had CFI earlier, 83 or 84 IIRC, but it depended on the transmission. 85 5 speeds were carbed/roller, 85 autos were CFI/flat tappet. 86 switched to multiport SEFI for both
I don't think the CFI cars were H.O.
 
Like a 'vette, there was a place to store it in the back. My dad had a black one with the moonroof.

I think those seats folded down, and there was a spot for the top... but I could be remembering a lot of other cars, lol. The T-top Firebirds were like that.
 
The car is a 1992 Sport with the 5.0 and M5R2 swapped.

Sorry for the lack of information, I have a rebuilt engine with holley heads and holley sniper efi that will eventually get a blower that I am swapping in for the 5.0 that came in the car.

My goals are to clean up the engine bay and remove all the wiring and circuits I don’t need as the ecu, have the battery and fuse panels in the trunk and I was thinking that rewiring the car would be a better idea than playing around with the existing harness and it would give me a change to clean up abit and run new wiring.

I was just wondering if anyone else had already rewired an mn12 that could help out.
 
I am planning on rewiring my whole car as I am switching over to Holley sniper efi and would like to remove as much wiring as I can and reroute the wiring to make things alot cleaner.

Will also be moving battery to the trunk and making a custom fuse panel.

Has anyone already done this or does anyone have any tips or information on doing this?

Having the wiring diragrams is essential.

On my latest project car, I redid the entire wiring for an EV. However, this car is 10yrs older and despite being a more advanced car than the tbird (Ferrari), it was still simpler wiring job.
- I stripped out all the ICE related circuitry, removed the unnecessary "check control computer" (fancy 80's speak for a panel that shows you when some light bulbs burn out), and rerouted the stock wiring from the fuse panel straight back to the new LED lights, for example.
- The result was a simpler harness built from the stock wires
- The trickiest thing to handle was that some circuits (ex: the horn) were ground triggered wires and the pop up headlight control didn't use limit switches but 3 relays. I ended up wiring in a seperater multi-relay PCB in a weatherproof box to handle these signal conversions.
-I also rewrapped everything with TechFlex which made the install look cleaner.
- My concern was that my fuse panel was very, very expensive, prone to burning out, and used lots of very old components (bosch relays that predate my birth and no longer available easily at autozone/etc). In the end, my new fuse panel cost $260 and I sold the original panel to some purist for $1800. Pure silliness but a win-win for both of us.


In comparison, my tbird is a track car. I kept some circuits (like the ABS power) but stripped down every unnecessary wire inside the cabin as a way to remove weight (ex: no more speaker wiring, wiring to the dome light, etc.).
- I just cut back every unnecessary circuit and wire at the farthest connector I could trace it back to upstream (ex: at the firewall).
- I also simplified the engine harness so it would easily come apart for engine replacement at one place and added a few additional wires that I needed (aftermarket temp sensors).

Sure, you could replace this wiring but I'm not sure anything you install will be "better" than either cutting out the unnecessary wires from the stock harness or just leaving the vestigial wiring in place.
- In your situation, at most I'd strip out unnneeded wiring and then add what few wires you need to go from the new ECU to the EFI/intake manifold/TB
- The stock wiring itself in the tbird is fairly well segmented: there's the wiring to run stuff on the chassis and there's the engine harness/wiring to the ECU. Very few wires go from the engine to other places (say a few sensors and a signal from the gauge cluster to tell the alternator to charge, IIRC).
 
I've always wondered: do you keep the airbags for racing?
 
No. If you have your harnesses installed correctly, you don't need them. Plus the last thing you want at 100mph is something blowing up in your face when you bump someone.
 
I figured they got pulled,but I didn't know. Ever heard of an airbag powered glitter bomb? That would fix a porch pirate. :rofl:
 
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